I agree 100% with Nick that InfoSight is the best way to go.
That said, I wouldn't want to miss the opportunity to introduce you to the Nimble PowerShell Toolkit. We describe it HERE on Nimble Connect.
With the PS Toolkit, this is a pretty simple task as well. You can use the following one-liner after connecting to a Nimble array:
Get-NSVolume | select name,size,vol_usage*,snap_usage* | ConvertTo-Csv > vols.csv
You then end up with something like this:
From there it's just a matter of summing.
Thank you, this is useful and I am surprised i missed the export. The only thing I noticed is that is seems to prune some of the info. In the export under Snapshot Used (GB), in the size in under 1GB, it reports as 0. In the web GUI same volume would shows SNAPSHOT SPACE Used 3.65 MB. Granted its such a small thing in the amount of data and I get it may not report things under 1GB, but those I would show the report to would question it and ask why the volume wasn't being snapshotted when it is and is consuming a small amount of data.